With the SoundTools app you can visualize real-time microphone recorded sounds and the corresponding frequencies.
Main tools are:
+Visualize real-time recording sound wave form and display dBFS (Decibel Full Scale) meter.
+View the real-time (FFT) frequencies of the recording sound. Show the main (dominant) frequency.
+Real-time audio / recorded spectrum analyzer. Measure the magnitude of an input signal versus frequency within the full frequency range of the instrument. Display frequency (Fourier) bins (buckets). In the settings one can change the number of requency bins to display.
+Real-time instrument tuner; calibrate your guitar, violin, piano, and other instruments. Display the current recorded frequency in Hz and the note closest to this recorded frequency.
+Play a 440 Hz A tone / note to tune your instruments.
+Measure in real-time the Sound Pressure Level (SPL) on your Android. SPL is in dB(A). This Decibel measurement is A-weighted and thus adjusted for human ears.
+A metronome which produces regular (latency free), metrical ticks (beats, clicks). The Beats Per Minute are from 1 up to 250 BPM.
+ Change the sampling rates.
+ Change the number of spectrum bars.
+ Change Linear or Db (log) scale.
+ Change the FFT Windowing function.
+ All graphics are drawn in real-time (normalized) with no delays!
+ Help in 4 languages; English (GB/US), Dutch (NL), French (F) and German (D)
+ Added spectrum peaks.
+ Added Linear ans Db (log) scale.
+ Added serveral FFT Windowing functions.
+ Update so it runs on Android 4.x (Ice Cream Sandwich).
+ Added display Grid.
+ Added peak value in display.
+ Added help in 4 languages; English (GB/US), Dutch (NL), French (F) and German (D).
+ Updated Credits & Help.
+ Stable app!